1. Field of the Invention
This invention relates to a resistance welding apparatus and in particular to an automatic welding apparatus which is advantageous in that welding operations can be achieved in such a manner that material to be welded will not produce any undesirable "jumping" or oscillatory motions during the welding operation. Also-the-present invention ensures that the welding operation can be carried out in such a manner that the materials to be welded will not exhibit any torsional effects.
2. Description of the Prior Art
Conventionally, an automatic resistance welding apparatus is arranged to have an electrode gun which cooperates with another electrode provided at the earth side to grasp superposed metal plates, metal wires, metal tubes or the like to be welded, so that a welding operation is carried out on the contact portions of the mutually superposed materials. Thus, when it is necessary to weld a number of points on the materials, it takes a long time to complete such welding on all of these points since the points must be welded one by one. Also, when the points to be welded are not arranged straight but are scattered, it is necessary to accurately position and positively hold the materials to be welded because they may be caused to jump up or oscillate unexpectedly during welding. Further, when the materials being welded are structurally different from one another, for example, in case of a combination of a plate member with a wire or tube member, concurrent welding is not possible due to the shape of the electrode tip, so that the welding process must be divided into several steps or a plurality of welding facilities are required for one welding cycle, resulting in the increased cost of facilities. In addition, when the material to be welded is a wire of large length, it may be twisted during welding.